The subject of the present invention is a safety device for sealing a test tube, which device comprises a sealing plug made of rubber, a resilient plastic material, or of any other, corresponding elastic material and fitted inside the mouth of a test tube, liquid being added to or removed from the test tube through the said sealing plug. For different purposes, bottles and tubes are in use which have been sealed tightly, e.g., by means of a rubber or plastic plug. If liquid is to be added into or removed from these bottles or tubes without removing the plug, most commonly the plug is pierced by means of a sharp needle connected to a syringe. When the needle is removed, the rubber plug is mostly still tight as the elastic force of the rubber seals the hole made by the needle into the plug. The case is the same in respect of plugs made of plastic qualities suitable for the purpose. The plugs used in prior art were, however, such that they could not be pierced by means of pipette tips of plastic or by capillary tubes of glass, which are to-day mostly used ^* in connection with the dosage of various samples or reagents.

The object of the present invention is to eliminate the above drawbacks, and the test-tube sealing device in accordance with the invention is mainly characterized in that the upper face of the sealing plug is shaped as substantially conically narrowing towards the bottom of the sealing plug, constituting a portion guiding the pipette tip or the capillary tube, and that a channel is provided between the tip of this portion and the bottom face of the sealing plug, through which channel the pipette tip or the capillary tube can be pushed, but which channel is, by the effect of the elastic force,

closed tightly when the pipette tip or the capillary tube is removed from the channel.

Thus, the resilient sealing plug of the test tube has a prefabricated channel for the pipette tip or the capillary tube, which channel opens itself when the tip or the capillary tube is pushed through the sealing plug at a certain point. When, for example, the sample has been transferred from the tip or from the capillary tube into the test tube, the tip or the capillary tube may, if desired, be allowed to remain in position in the channel in the sealing plug as held by the elastic force of the sealing plug. In addition to the possibility of adding a sample or reagent into the test tube through the sealing plug, sample or reagent quantities of desired magnitude can also be taken out of the test tube by means of a pipette or capillary tube. Such a safety test tube has several possible applications, and it may be used as such in connection with an individual laboratory test or as a part of some system or equipment as its fixed or detachable part, as an individual tube or as a matrix consisting of several tubes. In a matrix, the sealing plugs of the safety test tubes may be separate or interconnected, with the same distances from each other as the distances between the test tubes themselves.

The invention comes out more closely from the following description and from the attached drawings, wherein

Figure 1 is a sectional side view of a test tube provided with a sealing plug,

Figure 2 shows a situation in which the tip of a pipette has been pushed through the sealing plug of the test tube,

Figure 3 shows a situation in which a capil- lary tube has been pushed through the sealing plug of the test tube, and

Figures 4 to 6 are sectional side views of

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different alternative solutions for closing the conical space at the top of the sealing plug by means of a cap. The material of the sealing plug 2 is rubber, a resilient plastic material or any other, corresponding elastic material. The bottom face of the sealing plug 2 is most appropriately shaped plane. On the contrary, the upper face of the sealing plug 2 is shaped as substantially conically narrowing towards the bottom of the sealing plug, so that this portion 3 functions as a part guiding the pipette tip 5 or the capillary tube 6. A channel 4 is provided between the tip of the conical guiding portion 3 and the bottom face of the sealing plug 2. The channel 4 may be an open channel all the way through, or some portion of the channel may be closed by a thin film, which can be readily pierced by the pipette tip 5 or by the capillary tube 6. When the sealing plug 2 is fitted .in its position inside the mouth of the test tube 1 , the channel 4 is kept tightly closed by the elastic force of the sealing plug 2 as the outer diameter of the sealing plug 2 has been determined as appropriate for the purpose in relation to the inner diameter of the test tube 1.

The test tube 1 provided with the sealing plug 2 is suitable, e.g., for the assay of the haemo- globin of blood. In such a case, the test tube 1 contains K-cyanide (e.g. a buffered mixture of a K-cyanide solution and K-ferricyanide solution at a certain ratio) , and the test tube 1 is closed by an elastic sealing plug 2. In order to assay the haemo- globin of blood, a blood sample of desired magnitude is transferred from a tube containing the blood sample by means of a pipette or capillary tube into test tubes 1 containing K-cyanide. In the assay of haemo¬ globin, when toxic K-cyanide is used as the reagent, it is extremely important that the reagent.is safely ready-packed in the test tubes under factory conditions meeting the requirements of safety at work. If the agST-E*-

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laboratory personnel pipettes the K-cyanide into the test tubes and thereupon adds the blood sample into it and measures the reaction mixture in this way obtained by still transferring into a cuvette of a photometer, the personnel is under constant risk of K-cyanide poisoning.

As the K-cyanide has been packed in the factory into a test tube 1 , which is sealed by a sealing plug 2, no risk of poisoning can be caused to the laboratory personnel through the sealing plug 2. The use of the safety test tube 1 increases the safety at work so that the tip 5 pushed through the sealing plug 2 of the test tube 1 for the purpose of pipetting the sample can be allowed to. remain in its position in the channel 4 in the sealing plug, in the way shown in Fig. 2. The lower end 13 of the tip 5, which was dipped in the sample, then remains inside the test tube 1 , and the outside of the tip 5 portion remaining out of the test tube 1 is clean. In this way, the tip 5 allowed to remain in position in the sealing plug 2 of the test tube 1 cannot cause a risk of, e.g., hepatitis or any other infection for the laboratory personnel. After the measurement, the safety test tube 1 with the contents and together with the tip 5 can be discarded easily as a single unit.

Besides increasing the safety at work, the safety test tube 1 also increases the precision. When a capillary tube 6 is pushed through the sealing plug 2 of the test tube 1 in accordance with Fig. 3, the lower part 14 of the capillary tube 6 passes through the tight channel 4 of the sealing plug 2, and at the same time the channel 4 wipes the outside face of the lower part 14 of the capillary tube 6 clean of sample drops. Some of these sample drops on the outside face of the capil- lary tube 6 are gathered as drops 15 in the conical space 3 in the upper face of the sealing plug 2. There¬ by the drops wiped off the outer face of the lower part

14 of the capillary tube 6 do not drop into the reagent present in the test tube 1 , nor are they flushed by the reagent when the test tube 1 is being shaken.

When small sample volumes are concerned, an extra sample on the outer face of the pipette tip 5 or capillary tube 6 might cause an error of tens of percentage units in the dosage of the sample.

In Figures 4 and 5, the mouth of the test tube 1 is closed by a sealing plug 7, which has a channel 9 for the pipette tip 5 or the capillary tube 6 , similarly to the above. In the sealing plug 7, above the conical portion 8, there is additionally a cylin-

- drical portion 16 so that, after the pipetting of the sample, the conical .space at the top of the sealing plug 7 of the test tube may be closed by means of a cap 10 in the way coming out from Fig. 4. In such a case, any liquid drops remaining in the top part of the sealing plug 7, which have been wiped, e.g., off the outer face of the pipette tip, do not cause any risk for the workers or for the environment during further handling of the tube, such as shaking, incubation, measurement in a photometer, etc. E.g., serum samples are always dangerous owing to the risk of hepatitis infection.

In Fig. 5, the.sealing plug 7 and the cap 10 are made of one piece, and a narrow, elastic and flexible portion 11 is provided as connecting them.

In Fig. 6, a cap 12 closes the conical space 3 of the sealing plug 2 in a corresponding way, but the cap 12 is in this case connected to the mouth opening of the test tube 1, being separate from the sealing plug 2.

It is also possible that the cap 12 is attached to the test tube 1 itself by means of a narrow elastic portion, whereat the test tube 1 and the cap 12 are manufactured as a single step of manufacture, e.g. by extruding, out of an appropriate plastic material.

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